I'm trying to get a rough estimate of the rating of a
transformer.

It comes from an AKAI AT-M670L tuner. Transformer part number is
ST41007 TW; L350Y197H01; T 982 TK. No luck searching the web for
these.

Primary: 220 V / 50 Hz.
Secondary #1: 2 x 16.8 V loaded (2 x 5.75 ohm)
Secondary #2: 1 x 3.07 V loaded (2 x 1.5 ohm) (I guess for the VFD).
Fuses on secondary #2: 2 x 315 mA T
Weight: 252 g.
Windings size: about 25 x 25 x 15 mm.
Core size: about 42 x 33 x 22 mm.

Thanks in advance.

--
André Majorel URL:http://www.teaser.fr/~amajorel/
"Je regrette le Concorde. Au moins il vous amenait directement à
l'hôtel." -- Cyrano

In article , Andre Majorel wrote:
I'm trying to get a rough estimate of the rating of a
transformer.

It comes from an AKAI AT-M670L tuner. Transformer part number is
ST41007 TW; L350Y197H01; T 982 TK. No luck searching the web for
these.

Primary: 220 V / 50 Hz.
Secondary #1: 2 x 16.8 V loaded (2 x 5.75 ohm)
Secondary #2: 1 x 3.07 V loaded (2 x 1.5 ohm) (I guess for the VFD).
Fuses on secondary #2: 2 x 315 mA T
Weight: 252 g.
Windings size: about 25 x 25 x 15 mm.
Core size: about 42 x 33 x 22 mm.


I can't find where its in the S.E.R.

You find the voltage drop as you load the outputs individually. The total load
of all outputs will cut down on the added individual outputs. Measure the
output from no load to drop voltage 10-20%, then measure or compute
current.

greg

"GregS" wrote in message
...
In article , Andre Majorel
wrote:
I'm trying to get a rough estimate of the rating of a
transformer.

It comes from an AKAI AT-M670L tuner. Transformer part number is
ST41007 TW; L350Y197H01; T 982 TK. No luck searching the web for
these.

Primary: 220 V / 50 Hz.
Secondary #1: 2 x 16.8 V loaded (2 x 5.75 ohm)
Secondary #2: 1 x 3.07 V loaded (2 x 1.5 ohm) (I guess for the VFD).
Fuses on secondary #2: 2 x 315 mA T
Weight: 252 g.
Windings size: about 25 x 25 x 15 mm.
Core size: about 42 x 33 x 22 mm.


I can't find where its in the S.E.R.

You find the voltage drop as you load the outputs individually. The total
load
of all outputs will cut down on the added individual outputs. Measure the
output from no load to drop voltage 10-20%, then measure or compute
current.

greg


Given that the transformer is likely to be over 85% efficient, the input
power consumption rating printed on the back of the unit will give you a
good idea of the VA rating of it

Arfa

On 2008-09-23, Arfa Daily wrote:
"GregS" wrote in message
...
In article , Andre Majorel
wrote:
I'm trying to get a rough estimate of the rating of a
transformer.

It comes from an AKAI AT-M670L tuner. Transformer part number is
ST41007 TW; L350Y197H01; T 982 TK. No luck searching the web for
these.

Primary: 220 V / 50 Hz.
Secondary #1: 2 x 16.8 V loaded (2 x 5.75 ohm)
Secondary #2: 1 x 3.07 V loaded (2 x 1.5 ohm) (I guess for the VFD).
Fuses on secondary #2: 2 x 315 mA T
Weight: 252 g.
Windings size: about 25 x 25 x 15 mm.
Core size: about 42 x 33 x 22 mm.


I can't find where its in the S.E.R.

You find the voltage drop as you load the outputs
individually. The total load of all outputs will cut down on
the added individual outputs. Measure the output from no load
to drop voltage 10-20%, then measure or compute current.

Given that the transformer is likely to be over 85% efficient,
the input power consumption rating printed on the back of the
unit will give you a good idea of the VA rating of it

Well, there is none !

I expected you'd all take from the fuse rating. Interesting that
you didn't... (I made a mistake, BTW : the fuses are on the 16.8 V
windings.)

The measure-current-at-10-to-20%-lower-voltage-than-unloaded
method seems a little vague to me, not knowing what the V vs. I
curve looks like (I know very little about transformers).

Think I might as well increase the load until the transformer
becomes "too hot"...

--
André Majorel URL:http://www.teaser.fr/~amajorel/
"Je regrette le Concorde. Au moins il vous amenait directement à
l'hôtel." -- Cyrano

"Andre Majorel" wrote in message
...
On 2008-09-23, Arfa Daily wrote:
"GregS" wrote in message
...
In article , Andre Majorel
wrote:
I'm trying to get a rough estimate of the rating of a
transformer.

It comes from an AKAI AT-M670L tuner. Transformer part number is
ST41007 TW; L350Y197H01; T 982 TK. No luck searching the web for
these.

Primary: 220 V / 50 Hz.
Secondary #1: 2 x 16.8 V loaded (2 x 5.75 ohm)
Secondary #2: 1 x 3.07 V loaded (2 x 1.5 ohm) (I guess for the VFD).
Fuses on secondary #2: 2 x 315 mA T
Weight: 252 g.
Windings size: about 25 x 25 x 15 mm.
Core size: about 42 x 33 x 22 mm.


I can't find where its in the S.E.R.

You find the voltage drop as you load the outputs
individually. The total load of all outputs will cut down on
the added individual outputs. Measure the output from no load
to drop voltage 10-20%, then measure or compute current.

Given that the transformer is likely to be over 85% efficient,
the input power consumption rating printed on the back of the
unit will give you a good idea of the VA rating of it

Well, there is none !

I expected you'd all take from the fuse rating. Interesting that
you didn't... (I made a mistake, BTW : the fuses are on the 16.8 V
windings.)

The measure-current-at-10-to-20%-lower-voltage-than-unloaded
method seems a little vague to me, not knowing what the V vs. I
curve looks like (I know very little about transformers).

Think I might as well increase the load until the transformer
becomes "too hot"...

--
André Majorel URL:http://www.teaser.fr/~amajorel/
"Je regrette le Concorde. Au moins il vous amenait directement à
l'hôtel." -- Cyrano


If you do that, it might be the only time that you do, as it may well have a
thermal fuse embedded in the primary winding, which will likely fail. Open
circuit. Forever ...

What exactly is the issue with knowing the rating of this transformer ?
Apparently, it is working, as you are able to measure voltages. Worst case,
you could just measure the primary current with it running the tuner. If
it's a 'typical' little red transformer that is normally to be found in such
items, then just multiply the power consumption calculated from measuring
the input current, by about 1.5 to get a ballpark figure for the transformer
rating. When I say "ballpark", I actually mean in the same county, but maybe
not the same town ...

Arfa

In article , "Arfa Daily" wrote:

"Andre Majorel" wrote in message
...
On 2008-09-23, Arfa Daily wrote:
"GregS" wrote in message
...
In article , Andre Majorel
wrote:
I'm trying to get a rough estimate of the rating of a
transformer.

It comes from an AKAI AT-M670L tuner. Transformer part number is
ST41007 TW; L350Y197H01; T 982 TK. No luck searching the web for
these.

Primary: 220 V / 50 Hz.
Secondary #1: 2 x 16.8 V loaded (2 x 5.75 ohm)
Secondary #2: 1 x 3.07 V loaded (2 x 1.5 ohm) (I guess for the VFD).
Fuses on secondary #2: 2 x 315 mA T
Weight: 252 g.
Windings size: about 25 x 25 x 15 mm.
Core size: about 42 x 33 x 22 mm.


I can't find where its in the S.E.R.

You find the voltage drop as you load the outputs
individually. The total load of all outputs will cut down on
the added individual outputs. Measure the output from no load
to drop voltage 10-20%, then measure or compute current.

Given that the transformer is likely to be over 85% efficient,
the input power consumption rating printed on the back of the
unit will give you a good idea of the VA rating of it

Well, there is none !

I expected you'd all take from the fuse rating. Interesting that
you didn't... (I made a mistake, BTW : the fuses are on the 16.8 V
windings.)

The measure-current-at-10-to-20%-lower-voltage-than-unloaded
method seems a little vague to me, not knowing what the V vs. I
curve looks like (I know very little about transformers).

Think I might as well increase the load until the transformer
becomes "too hot"...

--
André Majorel URL:http://www.teaser.fr/~amajorel/
"Je regrette le Concorde. Au moins il vous amenait directement à
l'hôtel." -- Cyrano


If you do that, it might be the only time that you do, as it may well have a
thermal fuse embedded in the primary winding, which will likely fail. Open
circuit. Forever ...

What exactly is the issue with knowing the rating of this transformer ?
Apparently, it is working, as you are able to measure voltages. Worst case,
you could just measure the primary current with it running the tuner. If
it's a 'typical' little red transformer that is normally to be found in such
items, then just multiply the power consumption calculated from measuring
the input current, by about 1.5 to get a ballpark figure for the transformer
rating. When I say "ballpark", I actually mean in the same county, but maybe
not the same town ...

Arfa


Knowing the total rating gives little help determining individual windings.

On 2008-09-24, Arfa Daily wrote:
"Andre Majorel" wrote in message
...

Think I might as well increase the load until the transformer
becomes "too hot"...

If you do that, it might be the only time that you do, as it
may well have a thermal fuse embedded in the primary winding,
which will likely fail. Open circuit. Forever ...

Oh. My "too hot" threshold is probably at least 20°C below the
manufacturer's, though. g

What exactly is the issue with knowing the rating of this
transformer ?

Partly desire to learn what rules of thumb might exist, partly
that I'm going to reuse the transformer to power a few dual
supply circuits and want to know how much I can count on.

Apparently, it is working, as you are able to measure
voltages. Worst case, you could just measure the primary
current with it running the tuner. If it's a 'typical' little
red transformer that is normally to be found in such items,

It does have red adhesive tape around the windings.

then just multiply the power consumption calculated from
measuring the input current, by about 1.5 to get a ballpark
figure for the transformer rating. When I say "ballpark", I
actually mean in the same county, but maybe not the same town
...

Thanks.

--
André Majorel URL:http://www.teaser.fr/~amajorel/
"Je regrette le Concorde. Au moins il vous amenait directement à
l'hôtel." -- Cyrano

"GregS" wrote in message
...
In article , "Arfa Daily"
wrote:

"Andre Majorel" wrote in message
...
On 2008-09-23, Arfa Daily wrote:
"GregS" wrote in message
...
In article , Andre Majorel
wrote:
I'm trying to get a rough estimate of the rating of a
transformer.

It comes from an AKAI AT-M670L tuner. Transformer part number is
ST41007 TW; L350Y197H01; T 982 TK. No luck searching the web for
these.

Primary: 220 V / 50 Hz.
Secondary #1: 2 x 16.8 V loaded (2 x 5.75 ohm)
Secondary #2: 1 x 3.07 V loaded (2 x 1.5 ohm) (I guess for the VFD).
Fuses on secondary #2: 2 x 315 mA T
Weight: 252 g.
Windings size: about 25 x 25 x 15 mm.
Core size: about 42 x 33 x 22 mm.


I can't find where its in the S.E.R.

You find the voltage drop as you load the outputs
individually. The total load of all outputs will cut down on
the added individual outputs. Measure the output from no load
to drop voltage 10-20%, then measure or compute current.

Given that the transformer is likely to be over 85% efficient,
the input power consumption rating printed on the back of the
unit will give you a good idea of the VA rating of it

Well, there is none !

I expected you'd all take from the fuse rating. Interesting that
you didn't... (I made a mistake, BTW : the fuses are on the 16.8 V
windings.)

The measure-current-at-10-to-20%-lower-voltage-than-unloaded
method seems a little vague to me, not knowing what the V vs. I
curve looks like (I know very little about transformers).

Think I might as well increase the load until the transformer
becomes "too hot"...

--
André Majorel URL:http://www.teaser.fr/~amajorel/
"Je regrette le Concorde. Au moins il vous amenait directement à
l'hôtel." -- Cyrano


If you do that, it might be the only time that you do, as it may well have
a
thermal fuse embedded in the primary winding, which will likely fail. Open
circuit. Forever ...

What exactly is the issue with knowing the rating of this transformer ?
Apparently, it is working, as you are able to measure voltages. Worst
case,
you could just measure the primary current with it running the tuner. If
it's a 'typical' little red transformer that is normally to be found in
such
items, then just multiply the power consumption calculated from measuring
the input current, by about 1.5 to get a ballpark figure for the
transformer
rating. When I say "ballpark", I actually mean in the same county, but
maybe
not the same town ...

Arfa


Knowing the total rating gives little help determining individual
windings.


In theory, that may be largely true, but in practice, it will get you in the
area. The winding for the VFD heater can be largely ignored in the
calculation, as it will only be good for the few mA that the heater needs.
That leaves the two identical 'main' windings, and you wouldn't be too far
wrong, given what I said about ballparks, towns and counties, if you just
took the figure calculated from the primary current, and split it between
the two windings, half each.

Arfa

In article , Andre Majorel wrote:
On 2008-09-24, Arfa Daily wrote:
"Andre Majorel" wrote in message
...

Think I might as well increase the load until the transformer
becomes "too hot"...

Increasing load and watching voltage droop is much more effective and safe,
but burning it out is another method.

I didn't even read where the transformer came from, but it doesn't matter.



If you do that, it might be the only time that you do, as it
may well have a thermal fuse embedded in the primary winding,
which will likely fail. Open circuit. Forever ...

Oh. My "too hot" threshold is probably at least 20°C below the
manufacturer's, though. g

What exactly is the issue with knowing the rating of this
transformer ?

Partly desire to learn what rules of thumb might exist, partly
that I'm going to reuse the transformer to power a few dual
supply circuits and want to know how much I can count on.

Apparently, it is working, as you are able to measure
voltages. Worst case, you could just measure the primary
current with it running the tuner. If it's a 'typical' little
red transformer that is normally to be found in such items,

It does have red adhesive tape around the windings.

then just multiply the power consumption calculated from
measuring the input current, by about 1.5 to get a ballpark
figure for the transformer rating. When I say "ballpark", I
actually mean in the same county, but maybe not the same town
...

Thanks.

"Andre Majorel" wrote in message
...
On 2008-09-24, Arfa Daily wrote:
"Andre Majorel" wrote in message
...

Think I might as well increase the load until the transformer
becomes "too hot"...

If you do that, it might be the only time that you do, as it
may well have a thermal fuse embedded in the primary winding,
which will likely fail. Open circuit. Forever ...

Oh. My "too hot" threshold is probably at least 20°C below the
manufacturer's, though. g



By the time that transformer has got hot enough on the outside for you to be
getting worried, the windings in which the thermal fuse is buried, if indeed
it has one, will have reached the temperature necessary to open it. They are
quite delicate and it doesn't take much overload to **** them. I base this
assertion on 35 years of mending kit with them in.



What exactly is the issue with knowing the rating of this
transformer ?

Partly desire to learn what rules of thumb might exist, partly
that I'm going to reuse the transformer to power a few dual
supply circuits and want to know how much I can count on.



In the case of these little consumer-item transformers, rule of thumb is
about all you can count on. They are just about adequate for the job they
do, with everything working normally, which is all that the equipment
manufacturers need them to do. They are not too bothered about exact voltage
outputs or voltage sag, as they are invariably followed by 'good enough'
electronic regulation on the rails being produced from them. In the case of
your tuner, the current demand by the circuitry, will be pretty steady once
the processor has booted and all the filter caps have charged. If you want
to know what the transformer is good for, you could measure the current
drain on one of the secondaries with it running the tuner, and then add
another 30 to 50 %. I would be surprised if you couldn't draw an extra 80mA
or so from each winding, without serious sag problems. That's quite a few op
amps ...



Apparently, it is working, as you are able to measure
voltages. Worst case, you could just measure the primary
current with it running the tuner. If it's a 'typical' little
red transformer that is normally to be found in such items,

It does have red adhesive tape around the windings.



Ha! Knew it would ... d;~}



then just multiply the power consumption calculated from
measuring the input current, by about 1.5 to get a ballpark
figure for the transformer rating. When I say "ballpark", I
actually mean in the same county, but maybe not the same town
...

Thanks.

--
André Majorel URL:http://www.teaser.fr/~amajorel/
"Je regrette le Concorde. Au moins il vous amenait directement à
l'hôtel." -- Cyrano